Author(s): WHITNEY, K., SMULLIGAN, K., KEATING, M., CHRISTINO, M., MURRAY, M., KOCHER, M., MILEWSKI, M., HEYWORTH, B., DEJONG LEMPKE, A., Institution: HARVARD MEDICAL SCHOOL, Country: UNITED STATES, Abstract-ID: 2468

Background: Low energy availability (LEA), an imbalance between energy intake and exercise energy expenditure, is common in female athletes and may arise intentionally or unintentionally. Emerging evidence indicates that LEA impairs muscle hypertrophy, strength, and protein synthesis in response to physical training in healthy adult athlete populations, yet effects remain unknown in younger, post-injury populations.
Purpose: To assess strength and hop-test outcomes in the at 6-months after anterior cruciate ligament reconstruction (ACLR) among adolescent female athletes with LEA indicators (LEA-I) compared to those without (non-LEA-I). We hypothesized that those with LEA-I would have inferior neuromuscular outcomes.
Methods: In this retrospective case-control study, we included females age 15-21 years, with bilateral lower extremity isometric strength measurements and hop-testing at 6-months post-ACLR following standard rehabilitation. Athletes with multi-ligamentous or meniscal injuries, prior lower extremity surgeries, hormonal medication exposure, and/or polycystic ovarian syndrome were excluded. LEA-I were defined as menstrual dysfunction (i.e. primary and/or secondary amenorrhea, oligomenorrhea) and/or diagnosed eating disorder. Descriptive statistics were used to compare patient characteristics, and analyses of variance were used to compare group and limb neuromuscular outcomes (alpha=0.050).
Results: 224 participants met inclusion criteria, with 56 (24%) having LEA-I (age: 16.4± 1.3 years), who were matched by age and graft type to 56 non-LEA-I participants (16.7± 1.4 years). There was no difference in BMI (LEA-I: 22.5 ± 3.1 kg/m2, non-LEA-I: 22.6 ± 3.5 kg/m2 ; p=0.859), nor primary sport (p=0.402, X2=5.12), between groups. At 6-months post-ACLR, quadriceps strength was inferior among those with LEA-I compared to those without, on the operative limb (LEA-I: 4.05 ± 1.14 Nm/kg, non-LEA-I: 4.75 ± 0.81 Nm/kg; p<0.001) and contralateral limb (LEA-I: 4.26 ± 1.14 Nm/kg, non-LEA-I: 4.79 ± 0.70 Nm/kg ; p=0.004). Hamstrings strength was inferior among those with LEA-I compared to those without, on the operative (LEA-I: 2.18 ± 0.49 Nm/kg, non-LEA-I: 2.45 ± 0.68 Nm/kg ; p=0.019) and contralateral limb (LEA-I: 2.83 ± 0.63 Nm/kg, non-LEA-I: 3.31 ± 0.63 Nm/kg ; p<0.001). Operative limb timed hop test results were inferior among those with LEA-I (2.54 ± 0.54 sec) compared to non-LEA-I (2.34 ± 0.38 sec), p=0.028, while all other operative and contralateral limb hop testing (i.e. single hop, triple hop, crossover hop) was equivocal between groups.
Conclusions: Adolescent female athletes 6-months post-ACLR with LEA-I demonstrated inferior bilateral quadriceps and hamstrings strength, and inferior timed hop test results compared to age- and graft-matched non-LEA-I counterparts. LEA-I are prevalent among adolescent female athletes presenting for ACLR, and LEA may have substantial negative impact on rehabilitation and return to sport preparedness.